Surgeons may benefit from a real-time tracking and visualization system (RTVS), which can lessen their workload, reduce computed tomography (CT) radiation injury to the patient and hasten the progress of a brachytherapy surgery, according to a recent study. RTVS presents a novel contribution to lung cancer brachytherapy.

“[W]e established an RTVS as an integral part of the robot-assisted template location system, which enables the surgeons to distantly and accurately monitor the automatic template location to better perform a lung cancer brachytherapy surgery,” researchers said.

RTVS includes tracking and visualization components, with a quaternion-based iterative closest point (QICP) algorithm for higher accuracy proposed for the premised module of spatial registration. A series of experiments in a CT room validated the arithmetic accuracy of QICP and the clinical performance of RTVS.

Based on the spatial registration experiment, QICP consistently showed a distinctly higher degree of accuracy of 0.87±0.11 mm compared with the other two conventional algorithms. Assessed by tracking and visualization experiments, RTVS achieved a tracking accuracy of 1.05±0.05 mm position and 0.29±0.14 deg orientation. The time cost for template location, as well as CT scan times, were also substantially reduced. [J Med Devices 2019;13:011009]

“The system is developed with the application of treatment planning system software platform with good operability and sound workability,” researchers said. “Performances of RTVS have been verified by a series of experiments and results show that the system lends itself well to the application of a clinical practice.”

The QICP algorithm for higher accuracy was proposed for the first time prior to the construction of RTVS for the premised module of spatial registration, they noted. Compared with conventional quaternion and ICP methods, QICP consistently presented a wider applicability and greater practical accuracy with less computational time.

“Though there are lots of ways of improving ICP in the literature and they are more sophisticated than our research, they still have room for improvement, such as the result of convergence, computational time and accuracy,” researchers said. [Int J Med Rob Comput Assisted Surg 2018;14:e1877; J Adv Signal Process 2017;5;
IEEE Trans Pattern Anal Mach Intell 1995;17:820-824]

Furthermore, other improved ICP algorithms were applied to do the registration of nine points, and the results showed that their computation time was shortened. However, they converged to local minimum for six time in 10 tests on average.

“The proposed QICP algorithm can prevent the algorithm from converging to a local minimum and achieve a higher registration accuracy using fewer points,” researchers said. “Therefore, we believe that our QICP algorithm is superior to other accepted methods.”

“We are intended to integrate the RTVS into our telemedicine platform in the next step. And then the surgical experts can directly make treatment plans and control the robot to accomplish automatic template location remotely for brachytherapy through the internet. We are prepared to carry out further experiments in several cooperative hospitals on this project in the near future,” they added.